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package org.apache.juneau.http;

/**
 * Represents a parsed <l>Allow</l> HTTP response header.
 * 
 * <p>
 * Valid methods for a specified resource. To be used for a 405 Method not allowed.
 * 
 * <h5 class='figure'>Example</h5>
 * <p class='bcode'>
 * 	Allow: GET, HEAD
 * </p>
 * 
 * <h5 class='topic'>RFC2616 Specification</h5>
 * 
 * The Allow entity-header field lists the set of methods supported by the resource identified by the Request-URI.
 * The purpose of this field is strictly to inform the recipient of valid methods associated with the resource.
 * An Allow header field MUST be present in a 405 (Method Not Allowed) response.
 * 
 * <p class='bcode'>
 * 	Allow   = "Allow" ":" #Method
 * </p>
 * 
 * <p>
 * Example of use:
 * <p class='bcode'>
 * 	Allow: GET, HEAD, PUT
 * </p>
 * 
 * <p>
 * This field cannot prevent a client from trying other methods.
 * However, the indications given by the Allow header field value SHOULD be followed.
 * 
 * <p>
 * The actual set of allowed methods is defined by the origin server at the time of each request.
 * 
 * <p>
 * The Allow header field MAY be provided with a PUT request to recommend the methods to be supported by the new or
 * modified resource.
 * 
 * <p>
 * The server is not required to support these methods and SHOULD include an Allow header in the response giving the
 * actual supported methods.
 * 
 * <p>
 * A proxy MUST NOT modify the Allow header field even if it does not understand all the methods specified, since the
 * user agent might
 * have other means of communicating with the origin server.
 * 
 * <h5 class='section'>See Also:</h5>
 * <ul class='doctree'>
 * 	<li class='extlink'><a class='doclink' href='https://www.w3.org/Protocols/rfc2616/rfc2616.html'>Hypertext Transfer Protocol -- HTTP/1.1</a>
 * </ul>
 */
public final class Allow extends HeaderStringArray {

	/**
	 * Returns a parsed <code>Allow</code> header.
	 * 
	 * @param value The <code>Allow</code> header string.
	 * @return The parsed <code>Allow</code> header, or <jk>null</jk> if the string was null.
	 */
	public static Allow forString(String value) {
		if (value == null)
			return null;
		return new Allow(value);
	}

	private Allow(String value) {
		super(value);
	}
}
